As the fracas over the proposed federal anti-piracy legislation known as SOPA heats up this week, the open-source encyclopedia website, Wikipedia, says it will shut down for 24 hours, beginning midnight Tuesday to protest what the website warns is a threat to free speech.

Instead of its usual homepage, users who navigate to the English-language Wikipedia Wednesday will find directions for reaching local members of Congress to protest the Stop Online Piracy Act (SOPA) and the Protect Intellectual Property Act (PIPA). Wikipedia founder Jimmy Wales said in a statement Monday, he hopes this "will melt phone systems in Washington."

A House subcommittee was scheduled to prepare SOPA for a vote later this month. The Senate had planned a vote on PIPA even sooner. Now, it appears both votes could be delayed as some supporters in the House and Senate suggest they may be open changes in the bill.

The Wikipedia blackout is intended to spotlight the value of free and open access to information on the Internet, but it also underlies how fractious the issue is as it draws fire from both critics and supporters.

“SOPA is an unconstitutional, dangerous waste of time – that is, a violation of the First Amendment that won't achieve its ends, and could cripple the Internet with its provision that sites could be liable for any pirated material posted on their online premises,” says Fordham University media professor Paul Levinson via e-mail. No site can possibly police every post – text or video – for adherence to copyright, he says.